HOUSTON (AP) - The Texas prison agency’s position that its supplier of a new batch of execution drugs should be kept secret is being challenged by attorneys for two inmates who would be the first executed with the replenished stockpile.

An emergency hearing was set before a state judge in Austin on Thursday, a day after attorneys for convicted killers Tommy Lynn Sells and Ramiro Hernandez-Llanas filed a lawsuit demanding the Texas Department of Criminal Justice name the provider of the pentobarbital, the sedative the state uses for lethal injections.

Sells and Hernandez-Llanas are scheduled to die April 3 and 9 respectively. Sells was condemned for slashing two girls’ throats in 1999 at a home near Del Rio; one girl died. Hernandez-Llanas was condemned for the 1997 beating death of a man who owned a ranch where Hernandez worked near Kerrville.

“Time is truly of the essence,” the inmates’ lawyers said in their lawsuit. “Without information about where the drugs come from, and the purity, potency and integrity of those drugs, neither Mr. Hernandez-Llanas nor Mr. Sells can evaluate the risk that their executions will subject them to cruel and unusual pain in violation of the Eighth Amendment.”

The current supply of pentobarbital used for lethal injections in Texas expires April 1. Prison officials said last week they have a new supply but cited security reasons for declining to disclose the supplier’s name.

The state attorney general’s office previously has said the information should be public and is waiting for arguments from the agency on why the policy should be changed.

The dispute in the state that executes more inmates than any other comes as major drugmakers, many based in Europe, have stopped selling pentobarbital and other substances used in lethal injections to U.S. corrections agencies because they oppose the death penalty.

Texas only had enough pentobarbital to continue carrying out executions through the end of March until it obtained its new supply from the unknown provider. An inmate set to die Thursday would be using the sedative from that supply.

Department of Criminal Justice spokesman Jason Clark declined to comment Wednesday on the lawsuit, saying the agency “doesn’t comment on pending litigation.” Last week, he said department officials “are not disclosing the identity of the pharmacy because of previous, specific threats of serious physical harm made against businesses and their employees that have provided drugs used in the lethal injection process.”

Attorney General Greg Abbott’s office was set to represent the prison agency at Thursday’s hearing before State District Judge Tim Sulak, said Lauren Bean, a spokeswoman for Abbott.

The inmates’ lawyers said their filing compels Texas’ corrections department to comply with the state’s Public Information Act, adding that the deadline for the agency to submit its request for an attorney general’s opinion regarding the new secrecy is April 1.

“Even if (prison officials) expedited the filing of that request — which they have not said they will do — the attorney general will not be able to write an opinion before Mr. Sells’ April 3rd scheduled execution,” attorneys Maurie Levin, Naomi Terr and Hilary Sheard wrote.

On Wednesday, an Oklahoma judge voided that state’s execution law, agreeing with inmates that a “veil of secrecy” preventing them from seeking information about the drugs used in lethal injections violated their rights under the state constitution. Oklahoma officials plan to appeal.

Oklahoma is among the states that have promised companies confidentiality if they will provide the sedatives or paralyzing agents used to execute condemned prisoners, and went beyond that to prevent information from being revealed even in court.

Arkansas and Missouri keep execution information secret.

While Texas prison officials haven’t indicated they want to go to the extent those states have, they are seeking to at least keep the name of their lethal drug source from being revealed.

“We’re not in conflict with the law,” Clark, the Department of Criminal Justice spokesman, said last week. “We plan to seek an AG’s opinion, which is appropriate in a situation like this, and the AG’s office will determine whether it’s releasable.”